There has been put into practical use an imaging apparatus using optical coherence tomography (OCT) taking advantage of coherence of low coherence light (hereinafter referred to as OCT apparatus). The imaging apparatus can obtain a tomographic image with resolution on the order of a wavelength of light incident on an object, which enables providing a high-resolution tomographic image of an object to be detected.
Light from a light source is split into measuring light and reference light by a splitting light path such as a beam splitter. An object to be detected such as the eyes is first irradiated with the measuring light through a measuring light path. The light returning from the object to be detected is then conducted to a detecting position through a detecting light path. The term “returning light” refers to reflected light and scattered light including information on an interface in the direction in which the object to be detected is irradiated with light. The reference light is reflected by a reference mirror through a reference light path to conduct the reflected light to the detecting position. The detection and analysis of the coherent light of the returning light and the reference light with a detector provides a tomographic image of the object to be detected.
Japanese Patent Application Laid-Open No. H11-325849 discloses an OCT configuration in which the position of a reference mirror is discontinuously changed three times in measuring one point of an object to be detected to obtain wavelength spectra and then the calculation of the spectra provides a tomographic image.
Furthermore, there is disclosed a Fourier-Domain OCT apparatus (hereinafter referred to as PD-OCT apparatus) in which wavelength spectra are obtained with a reference mirror of the OCT apparatus fixed and a tomogram is measured by Fourier transformation, in a paper; A. F. Fercher, C. K. Hitzenberger, G. Kamp, S. Y. El-Zaiat, Opt. Commun. 117, 43-48, (1995). The FD-OCT apparatus includes a system using a spectroscope (SD-OCT: Spectral Domain OCT) and a system sweeping the wavelength of a light source (SS-OCT: Source Swept-OCT).